1. Field of the Invention
The present invention relates to a convertible washing machine having a tub tiltable from a vertical position to a horizontal position to selectively perform the pulsator type washing and the drum type washing, and more particularly to an apparatus for and method of determining a tilt angle of the tub in such a convertible washing machine, capable of controlling the tub to be positioned at various tilt angles such as 90.degree. corresponding to the vertical position, 0.degree. corresponding to the horizontal position and 45.degree., thereby enabling the pulsator type washing, the drum type washing and the small load washing.
2. Description of the Prior Art
A "convertible washing machine" means a washing machine having a tub tiltable through an angle ranged from 0.degree. to 90.degree. with respect to a tub shaft so that it can performs conventional pulsator type washing at a tub tilt angle of 90.degree. corresponding to the vertical position of the tub and a conventional drum type washing at a tub tilt angle of 0.degree. corresponding to the horizontal position of the tub.
FIG. 1 is a partially-broken elevational view of conventional convertible washing machine. In FIG. 1, the reference numeral 1 denotes an outer case, 2 an outdoor, 3 a cover, 4 a base plate, 5 a rear cover, 6 a damper, 7 a pulsator motor, 8 a drum pulley, 9 a pulsator pulley, 10 a damper bracket, 11 a tub, 12 a drum motor, 13 a bearing housing, 14 a tub shaft, 15 a worm gear, 16 and 16' switches, 16a and 16a' respective leads of switches 16 and 16', 17 a worm motor, and 18 a worm.
As shown in FIG. 2, the worm gear 15 has a pair of stoppers 20 and 20' respectively formed at its opposite ends, and a pair of mounting holes 19 and 19' perforated through its inner portion having no gear tooth.
The worm gear 15 is fixedly mounted to the bearing housing 13 by means of the mounting holes 19 and 19'. The worm motor 17 is fixedly mounted to one side portion of the tub 11. To the worm motor 17, the worm 18 is rotatably coupled.
A tub tilting operation and a tub tilt angle sensing operation performed in the conventional convertible washing machine will now be described.
As the worm motor 17 drives under a condition that the tub 11 is kept at its vertical position corresponding to the tub tilt angle of 90.degree., as shown in FIG. 1, the worm 18 rotates by the drive force of the worm motor 17.
By the rotation of the worm 18, the tub 11 rotates about the tub shaft 14 toward its horizontal position because the worm 18 is engaged with the worm gear 19 fixedly mounted to the bearing housing 13.
Once the tub 11 rotates through an angle of 90.degree., that is, when it is positioned at its horizontal position corresponding to the tub tilt angle of 0.degree., one end of the worm 18 pushes the corresponding switch lead 16a', thereby causing the worm motor 17 to stop.
When the tub 11 is desired to return from its horizontal position (0.degree.to its vertical position (90.degree.), the worm motor 17 drives reversely. By the reverse drive force of the worm motor 17, the tub 11 rotates toward its vertical position in the same manner as mentioned above.
When the tub 11 reaches its vertical position (90.degree.), the other end of the worm 18 pushes the corresponding switch lead 16', thereby causing the worm motor 17 to stop.
However, this tub tilt angle sensing device equipped in the conventional convertible washing machine has several problems as follows.
First, the switches 16 and 16' and the stoppers 20 and 20' of worm gear 15 may be easily damaged because this conventional tub tilt angle sensing device is constructed to physically push switches 16 and 16', respectively, by both ends of the worm 18. Even after the worm motor 17 stops, the rotation of the tub 11 is continues due to the inertia of the rotating tub 11, thereby causing the worm 18 to strike against the leads 16' forcefully and 16a'. This causes damage to not only the switches 16 and 16', but also the stoppers 20 and 20' of worm gear 15.
Second, it is difficult to always maintain the tub at a desired tub tilt angle. Where the quantity of clothes to be washed is small, the washing operation is often carried out under a condition that the tub is maintained at a tilted position by an angle of about 45.degree. so as to reduce the amount of washing water. In this case, however, it is difficult to always maintain the tub at a desired tub tilt angle.
Third, it is impossible to detect whether the current tub position corresponds to the horizontal position (0.degree.) or the vertical position (90.degree.) when the electric power once cut off is applied again.